Significant advances in presentation technologies have occurred in recent years. Workstations with sophisticated user interfaces--long the sole domain of engineers and scientists--now are finding application in the broader marketplace.
New presentation software and standardization efforts have bolstered this migration to a larger commercial environment. X-Windows software from MIT and its X-Consortium are illustrative of such development. The combination of X-Windows with other standards, such as OSF/Motif, UNIX and C, has allowed application developers a new freedom from many platform issues and has enhanced the efficiency in the creation of user interfaces (UIs).
In spite of such strides in efficiency and much continuing work in X-Windows, one of the most time consuming tasks in creating working UIs has received little or no attention--the development of software to control the screens a user sees and the sequence with which those screens are presented. Throughout this disclosure, this type of software is referred to as navigational logic.
Currently, the only mechanism provided within X-Windows and many other environments to accomplish navigation is through what are generically referred to as "callback" routines. That mechanism provides a means of linking the processing of a function to an X-Event such as a button push or the filling in of a field on the screen.
With callback functions it is possible to achieve certain navigational goals. For example, a callback might be executed from a button press in the current screen which unmaps that screen and presents another subsequent screen. The approach has value, but it becomes cumbersome when the navigational logic is more complex than simple screen-to-screen traversal.